Airplane



G. M. BELL NcA I 7 2,135,096

- AIRPLANE Now 1 Original Fil ed March 22, 1934 y s sneets-shet 1 Patented Nov. 1, 1938 I .Appllcation'March 22,

This invention relates to improvements in airplanes, and more particularly'to improved flaps and combinations of airfoils and flaps:

The advantages of a high lift c'oemcient duringj landing and takeoifs, coupled with a reduced '00-: efficient during normalflight, have longbeenape t preciated by airplane designers. Many s'ugges-u I tions have been advanced as to'the bestmethods combinations shown -in dreams adde 1 described in the specification; it being understood that these'combinations are given asillustrative of the principle involvedrather than'as restrictive definitions of given; mechanism.

r In ordertomor'e clearly explain the invention,

physical embodiments are shown in the accomof attaining these results. of themany proposals v there are two which have-achieved not an incon siderable success in actualpperation. "These are the slotted wing and the flap.

is that the wing surfaces are made more concave,-

" giving in effect a highcainbered 1wing,and 'resultingin an increase in lift. This is true whether a leading edge or a trailing edge-flap is considered. a

The change in curvature is of course greatly ac-'-- centuated if both a leading and a trailing edge 'fiap' are mounted on the onewing.

Upon operation of a fiap,-a concomitant of the 'increasedlift is an increased drag.- This, however, is a real advantage, for the increase in drag permits a steeper gliding angle at lower landing speeds. I While the utilization of a flapdoes present some advantages, they are notwithout inherentdisadvantages. The employmentofthis extra mechanism naturally adds weight to the plane. It has been found also that when the flaps are moved to $5 cult to control; Aniajorireason" for this is that:

' as the flap is depressed,the center of pressure on the wing is displaced. This of course is a decided disadvantage, inasmuch as it'changes or modifies the balance of the airplane. Another drawback in the rear of the trailing edge of the wing is. disturbed or rendered more turbulent,- andthis Y considerably reduces the eii'ectiveness'of; the empennage surfaces and particularly the stabilizer.

It is-an object of the'present invention to improve the operation of arrairplane by utilizing the split flap principle and correlating this with other factors. of design." Another object is to provide an airplane in '50 which flaps are associated in a novel manner with control surfaces. r

Another object is to provide a novel type of wing cellule' utilizinga split flap.

improved-type ofaileron; v

panying drawings, in" which:

1 Figure 1 is atop, plan view, ofone type of plane embodyingthe principles of the present invention. 10

Figure 2 isa front e'levationof the plane shown ,in Figure V The flap, so called, inits broadest aspect is in efiect a device which changestheeflectivecurva ll ture of the wing; When'theflap is operated by being opened downwardly of the wing,-the result 1 Figure :3; isqa nt enlarged on line 3 -4 of'Figure 2. a a

' nite-:4 is ajtop structureshown in Figure 4; a

Figure 'l. is a .plan'view of yet another modification of the invention,- utilizing' the flap and an 1Figure 8 is a front elevation in-Figure'l. a 1 Figure 94s an enlargedcross sectionaldetail taken-lioniline 18--8-of Figure 8.2.v i Figure lOis a top plan view of yet another type of wing cellule embodying .the present invention.

Figure 11 is a front elevation of the part shown ofithe device shown I in Figure-.10.

. line l2-v-l2 of Figure 11. a v the operative position theairplane is more diflii Figure 12 is an enlarged cross section talren on Figure 13is a planview of a wing cellule some- -whatsimilarto that shown in Figure 10; v

of such flaps is that uponoperationthe air flow f Fig; :15 is an enlarged cross section taken on" Fig. .16 is a plan view of yet another modification 40 of the invention.

The fundamental concept. of .the presentinvention is to obtain the advantagesimdlap operation,

while using asimpleform ofisplit fnap, and yet obtain optimum eflect fronethei'controlsurfaces such as theailerons. Within the spirit of the present inventionf'are comprehended a number of "different specific arrangements of 'Sombinations whereby thisresult may be secured,-. namely the flap operation,

retention of full effectiveness of aileron surraces while'nevertheles's securing the full advantagesjnl It is known to those smned in the irt-tha one of the disadvantages of the incorporation offiaps upon airplanes has been the undesirableeffect plansection of an improved 15 wingwcellule. 1 g

Figure 5 is, anielevationof the;portion of the ture' but also their operation to counterbalance or nullify the disadvantages of the flap. This principle will be more readily comprehendedupon a consideration of several mechanical structures in which these advantageous results are secured.

As shown in Figures 1, 2 and 3,. the ,advantages 1 of split flap operation may be secured without any drastic modifications of the main sustena tion surfaces by utilizing a new type of controlsurface and byproperly positioning this with respectto the location of the flap. In order to clarify and simplify the description, there are --shown in the drawing only those'portions of an airplane which are essential to an understanding of the invention. "In all of the. =flgures, merely a 1 structure arew'ell known to those skilledin the:

portion of the-fuselage and the wing surfaces are shown. It will be understood, however, that these-- figures are intended to illustrate a completely op.-.

erative machine- The; conventional elements such as power plant, propeller, and empennage art, and are contemplated here; I

As shown in Figure l, anairplane made=in accordanc with the present'invention may com,-

- strut wing3 is of airfoil form and is provided with,

prise a fuselage I provided with the essential ape pendages, not shown;' Suitably secured to the fuselage are the main wings 2. Preferably-these are secured atan upper portion of the'fuselage.

Secured to a lowerportion of thefuselage and extending upwardly ata decided positive dihedral 1 angle are the strut .wingsi a'ndL: Preferably these terminate shortof the underside of the wings and are attachedto thezwings bysuitable,

tension means 5 and bracing means 6; Thefront suitable structural elements such as..spar's and xribs, whereby its functions'as a strutand also as an, airfoil are-subserved. The lift strut 4 may be of'the same general design as the'lift strut I,

- but differs from it in being mounted for rotation about the axial. The main wing is constructed.

Ill

without ailerons, but is provided with the-flap I.

the: flap 8 to the cockpit,.by.reason of which the flapis operated. .As shown in Figure 1,the flap:

may extend the full span of the wing. If deas showngmay be of any desired configuration. It

is to be observed that the'main wing 2 is not providecl with the usual type of aileron. ,Controlis secured by utilizing the lift struts l as ailerons,

'By rotating these about their axes on one side that themember 4 subservesa number of func= tions. In the first place, in normal horizontal flight it actsv as an air sustenation surface, add- 7 ing materially to the lift ofthe-plane. In an angle ofbank, due to itsdihedral setting, its horizontal equivalent increases and thus imposes automatically increased lift on the-low side. By rotating this member about its axis, its angle of will immediately be perceived .by those skilled in in the center of pressure ,of the wing 2. shift tends to unbalance the plane. In the'prescompensate for the shift in the center of pres- -position onthe main sustenation surfaces and a relatively low position of the ailerons, the maxiincidence may be varied and the effective lift thereby changed to serve as a control surfaceor aileron. 3

It will'be appreciated that by utilizing such a member, the incorporation of the flap and the 5 utilization of the flap principle becomes relatively simple. In a sense, the aileron l is considerably displaced from the iiap and whatever the position ofthe flap a smoothuninterrupted flow of air over the aileron 4 obtains. If desired, it will be appreciated that each lift strut 3 and the lift strut 4 may be employed'as control or aileron surfaces. The method of connecting these up for simultaneous operation to perform this function the art. If desired also the aileron 3 may be mounted for rotation and utilized not as an aileron but as ameans for compensating for the "shift in the center of pressure on the wing 2, due

vsuits. However, a-concomitantof this increased" liftand/or the change of the curvature is a shift This ent invention. 1 however, this unbalance 1 is com- .pensa ted for and equilibrium attained by'a' cor- "relation of factors including the effect of the downwash on the, tail surfaces, due tothe operation of the flaps, and the rotation of the supplemental wing {about its axis. It willbe observed therefore, that this type of'plane provides for improved operation. The main wings 2 may may be spaced above; the fuselage and suitably secured' to it through the medium. of cabane .struts. By positioning the main wing high on the fuselage or by spacing it above the fuselage, it will be appreciated that the depression of the traiiing flap will increase the downwash on the tail surfaces thus imposing a-fo'rce tending to sure on the main wing. With this is correlated the position and/or movement of the airfoils 3 V and l which serve. further to minimize the longitudinal unbalancing effect due to the operation of the. flaps. By employing this relatively high mum control effect of the ailerons is secured whatever the position of the flap.

. i t. .The major advantages abovepointedoutmay' I die secured with other and specifically different sired of course the flap may be terminated short,

of the wing span, and instead of being rectilinear,

structures. An example of such structure is shown in Figures i, 5 and 6. In these figures, as

in Figure l. the structure includes the fuselage I, :with which are'associated the necessary elements (not-shown) such as landing gear, power plant and propeller, empennage units and so forth.

-. Similarly to the device shownin Figure l, the

airplane shown in Figure 4 is provided with the main wings {which are properly filleted at the 65 nates short of theunder surface of the main wing as at i I and is securely attached to structural ele- 74 mam merits of the wing suchas the spare; byzthe se-.

curing means I! and 'l3. -Theiwingzmay befof is'not as eificient as is the short aileron in producing a roll for a given angle of throw, never-v "fi theless it is very effective for all practicalipurie poses and has the advantage 1 of requiring 'lessl effort onthe partof theipilotj due to the smaller appreciated that the effective area of the' wing III aileron area ratio. s

' area ofthe center'of pressure of the aileron wing.

The operation of'thi's type'-of=-airplane is, in

essentials; the same-as that shown in Figure 1. The: actuation of the flap 8 increases the lift on the wing 2. As pointed out hereinbeforeydepres-t' 'sion of the flap materially increases thedowne' wash onthe tail 'surfaces 'which thus "compena 1 sates in some degree -fortheshlft in the'center of'press ure on the main wing.- Further compena sation ornuilification {of thisshift in pressure f is secured due to the position and or. potential movement of the'airfoil I; Thus full effectiveness of the longitudinal control surfaces is sethe entire plane; "It is to lie-observed also that the aileron wing in 'is-located within the vertical" plane including the shifting center of pressure of the main wing 2. This aileron wing therefore "inlthe device showninl lgures *7, 8 and9;

this device memamwmgz-is attached as de-.'.

. scribed to the fuselage i. This main wingis,

provided with a nap 8- extending any desired;

wing isastub wing'section l5'and' the positive dihedral'section "I61" The wing cellule-may be additionally strengthened by utilizing inter plane braces asindicated at I1; As shown inFigure '7;

l f the wing section It i's-preferably tapered toward "the tip and islsecured to the'underside of the In the device shown in Figures "7,

this particular'case the/aileron leis mounted position above the wing by means of the means of actuating mechanism extending to the cockpit. By positioning the aileron above the.

wing and the flap on the lower surface, it will; be appreciated that operation ofthe flap does not materially affect the air flow over. the aileron; "and hence does not diminishits efllciency. Such,

ajcombinatio'n ofi'flap anda displaced-aileronis :tm- MWM o V ,bothwithrespect to size and attitude, as to V 8-and9 the j aileron surface is displaced from the main wing.

In at a n aileron braces 19." Theaileron may be'rotated' by made, particularlyeflective in a plane of, the,

Thelift strut I8 is so designed,

compensatev for the shift in the centerofjpressure on ,the main wing a due, to" the operation of described. this compensation, is correlated .withthat resulting iron: the effect of l the ;downwash;on the surfaces due to the operation of flap combination, therefore, in eifect comprises ,a wing ceiule in which a flap {is operative but in; which an airfoil of appreciable -provided, the center of pressure of which is substantially unaifected by moments about the hinge pin. It will readily be thee-operation oirthe zflap on the main wing. It

':;will thusbe; understood by those skilled in the may be modified by a designer to'confo'rmto his particularg' ideas as to the mosteffective wing- ::v

art that theinitial setting of the .wing sections li andjimay bem ade withrespect to the shift i v l l gin the center of pressure orrthearea of the center The wing Ill ismounted for rotation on the axisil which is'shown as 'approximate'lyvin the of pressure; of the main wing,the areaof the center as modified by a the effect I of u the. downwash. due tothe operation of the flap. This type of structure, therefore, largely ,mini'miz'es "one of the outstanding disadvantages" of the flap, namely,- its eifect in unbalancing the plane due to the tshift'in the center of pressure on the wing asto maintain its-full eifectivenesa'despite the positionohthe. flap, 8. Ashes, been previously described,- the lift strut lfiilmayibe mounted for -rotationalong its chord and maybe operated eithermanuallyorautomatically to vary its'angle cured. By rotating the strut wing in on one side of the plane to properly change its angle of irrcidence; a rolling moment may be imported to qthe unbalance effected by the operation :of the A .flap. A a

Yet other types off apparatus may: be constructed .whichinclude the novel principles of the ,-presentinvention.r An example of such a :structendsto minimize the tendency of an unbalanced condition dueto the change inthecenter "of pressure.

Another method of securing the full advantage (if-the ilap' while yet retainingthe maximum: effectiveness of the aileron surface is illustrated"? ture isshown in Figures 10, ligand 12. in

and a lift; strut l5 connected at one' end, to the under side of the main wing and at the other to the-. stub wing section 15$; Iffdesire'd, the wing l cellulev may be rigidified by using, ;the inter-plane bracing members ii. ln tl is types bf-lplane, as in; the. others the aileron-is displaced a sufflcientdistance from'theflap to, insure its eflicient length of the spam: Associated with the main operation, regardless of ti' e position of the flap. One method of accomplishing this, as shown particularly inFigure 12, is to mount the split flap:

8 upon the underside of the main wing 2. l The ,iv otally connected at thef-tf ll g edge of the strut airfoilv 4 6. aileron maybe .hinged to this strut, in, thegusual naher. and loperated by conventional mechanism; Sinc'ethe lift strut is of ratherlarge area-,it readily be perceived that bymounting ailerons vat the" trailing portiono! the liftjstrut sufiicient control area may :becsecured; It will be observed that this type rofplane presents improved operation. When the .plane isinnormal horizontal flight in the air andthe split flap 8 1s closed,- bothjll wing sections, I and li'contribute tothe lift The wing lsectionii; {due to its dihedral setting, tends to render the plane, automaticallystable and materially checks sidesllp, t Lateral control or maneuverability of the pianeislsecured by operatingflthe ailerons lfl in the usual manner. As

noted above, the rolling moment development by pressed, the effective lift of the upper wing 2 is increased. Any turbulence or disturbance of air H w bodying twoor more struts, such for example as is shown in Figure 1. In such cases, one or both of the lift struts maybe mounted for rotation .so as-to jointly serve as ailerons orcontrol surflow caused by the flap; 8 has" no material "effect upon the "aileron 2ll,.due to theratherwide spacing' of displacement of these two," Y o It will be observed from the showing in Figures.

" 10 and 12 that the aileron 2ll extends to a positionouite close to'the-underside of the'mainwing;

. 25' g wing settingbf the wing section l6 maybe es- It will be understood-that this position" may be varied within rather'wide limits, depending *upon the desires of the designer. It'will be observed that a-device is shoWnin Figures-IO to 12 in which the aileron extends 'close'tothe upper wing and that whenthe aileron is in the up positionthe air flow'isrestrictedand' there is thus produced a desirable yawing efl'ect. -It will also be observed'jthat in this structure as in the others, the wing surface [6 may be so positioned with respectto-theupper wing 2 as'to largely compensate for the shiftinj the center of pressure on the main 'wing 2.];In other words, the

tablished not only with regard to its effectivesection I6 is largely within the vertical-plane of the center of pressureof the: main wing. x j The fundamental advantages" of an airplane 'ness as a wing surface, but also its effect in stabilizing the airplane-when the flap} is operat'ed. This effect can be made 'quitemarked,

particularly in view of the fact'that' the wing constructed as shown in Figures 10, 11 and 12 may be secured in another'manner, suchfor example as is shown in Figures 13, 14, and 15. In these figures the airplane comprise's the fuselage I, main wing 2, stub wing l5 and lift'strut l6.

'The" main winginay be considered a "conventional wing formed with the conventional aileron "2G mounted,;asshown,"at the trailing edge of the main wing for an app 'jeciable portion'of its span. I This aileron is operated by controls well' known to thoseskilled inthe art. The lift strut" l6; and if desired the-stub wing l5,are-provided I with the'split flaps 2| and 22. These flaps may be of conventional form and are pivotally mounted' upon'a-structural element of the airfoil sur-w face. 'Inthis type of construction, it will imme-. diately be perceived that the advant'ages of flap operation aresecured while yet maintaining the.

' full efiect of aileron operation. The-wing sec- 'tion l5 occupies a relatively-low position on the fuselage and depression of'the flap'22 below this wing surface does not materially aii'ectthe air flow over the stabilizer aud t elevator. i-The flap 2| "on the wingsection l6} while occupying a higher position; is nevertheless spaced quite: a. distance-laterally of; the fuselage, hence burbling or turbulence caused by operation of the flap .2.I'

does not" 'aifectjthe air flow "over the empennage structure toanyconsiderable extent;

j While the flap12l' has beenshown as of rela- 1 tiv'ely small dimensions and being mounted on 'the rear spar of the Winge1ement"|6, it will:' readily be appreciated; that it may beof any desired size and" shape. It will be further understood that the flaps 2| and 22 on each sideof the plane may be operated simultaneously or separately and successively. In" the device shown in Figures 13, 14 and 15, 'the operation of theflap will of coursecause a "shift of the center J of pressure above'the' wings "15 'and I6. Since,- however, the centerof'pressure on the main wing balance of-the plane is not seriously affected.

While the structures shown in Figures 4,7,

f and 13 'includea single 1m strut, it willbe'under stood that the principle of operation involved in these apparatus maybeutilized on planes emfaces,, or, as described, one may be employed as an-.aileron and the other'may be availed of as a means of automatically restoring the longitudinal balance of the-plane due to the shift in the center; of pressureonthe wing onwhich the flap is mounted. .l v a In the devices shown in Figures 1 to 15, in-

in the caseof Figure9 they aremounted on the same wing member and. relatively ,widely spaced. It will be'appreciated that the major advantages of the. present invention may be secured with yet other structures such as onein which the split flap, and the aileron are mounted on the same main wing; An example of such structure is shown in Figure 16. In the deviceshown in this figure, theairpiane may include thefuselage I; the; upper main wing 2 and thelife strut 3.

. l The root section of the main wing is. provided E with the splitflap 23 suitably pivoted to a structural part ofthe wing, and the aileron 24' is mounted for pivotal movement at the outer or tip end ofthe wing. I

It will be seen; that the major factors of opera- .tion hereinbefore described applyin the present case. By properly positioning the lift-strut 3 with respect to the normal center of pressure of the main'wing and properly correlating its wing setting, it will be appr'eciatedthat material shifts inthe centerof pressure on the main wing, due

tothe operation of the flap, can be in a large measure compensated.

.Whilein most of the figures of vthedrawings V .a high wingmonoplanehas, been described, it ;will'be understood that the, principle described hereinmay be utilized with a low wing monoplane. In such circumstances, ,the. main wing may be attached to a low part of the fuselage and strut wings 3 may be secured to the upper part .of the fuselage and extend downwardly at ,a negative dihedral angleto be attached by suitable meansto the upper surface of the main low .wing'; In other words,-;in a sense, they position of the main and strut wi ng shown, for example, in Figures 1 and 5, may be inverted or reversed.

Itwillalso be appreciated that in a combina- .tion: of the characterdescrlbed, additional beneflcial functions are obtainable. For example, the lifts'truts may bepivoially mounted at the fuselageand-at or near their tip end, so as to be rotatable. The lift struts'maybeconnected to controlmeanswithinthe cockpit and the mounting. of the lift struts, and the associated control means may be so correlated as'to utilize the lift Lstrutsas floating ailerons. In thesecircumstances, maximum aileron control is secured even athigh or exaggerated angles ofgattack when the mainn-wing approaches its position of vminimum "lift.

Itwill be understood that within the scope of the present invention any. desired type of flap may be employed- The flap 8 shownin the severalfigures in thezdrawing comprises a member, :nested inits inoperative-position, withinthe conaiaaooe I 3 5 tour of the main wing and pivotal about a point on the main wing. This nap. however, may be spaced from the main wing and may be of a compound movement type.- In short, any desired type or character of flap maybe employed herein. It will be manifestgthat in all of the modifications shown the fundamental principle is' the same, namely, the concffiot of securing'fullvalue from flap operation whilenevertheless utilizing to the greatest possible degree the control surfaces. In some circumstances, as has been described, it is possible to aggregate with these advantages the further advantage of an optional or automatic restoration of longitudinal balance by compensating for: or nullifying the eflectof the shift in the center of pressure on a wing carrying a flap;

Thereforerwhile specific embodiments of the invention have been described; it is to be understood that these are given merely as illustrative of. the principle involved; the specific structures shown are given merely to typify the embodiment of such principle and not as definitions-of or 1 limits upon the scope of the invention.

I claim: 1. An airplane comprising a main wing section on each side of the fuselage, a split flap-pivotally mounted on each section; a plurality of airfoils mounted on each side of the fuselag'e andattached respectively to the underside of the mainf' wing and to the fuselage, means to change the attitude of one of said airfoils to impose arolling.

moment on the airplane, and means to change the attitude of the other said airfoil to c'ompensate for changes in the center of pressure on the main wing due to theoperation of the flap.

and means to independently rotate the lift struts to vary the lifting effect of the struts soas to imjpose a predetermined rolling moment on the plane and to compensate for changes in the center'of pressure of the main wing due to the operation of the flap.

3. An airplane comprising a fuselage, a main wing section attached to the upper portion of. the

fuselage at'each side thereof, a plurality of 'sub-' s tantially parallel independently rotatable'strut wings oneach side of tha fuselage and attached respectively to a lower portion of the fuselage and to the underside. of the main wing; a split flap pivotally connected to the main wing and being so positioned that downwash therefrom reacts upon the horizontal stabilizer of the plane, and

means to change the lifting effect of one of the strut wings to impose a rolling moment-upon the plane and means independently to change the attitude of the other strut wing and compensate for changes in the center of pressure on the main wing "due to the operation of the flap.

a -GIUSEPPE M. BELLANCA. 

